Fiber cuts, equipment faults and degradations cause a significant number of disruptions and outages. As businesses and consumers become increasingly intolerant of network failures, downtime can be very expensive to carriers due to both lost revenue and tarnished images. As a result, carriers continually search for better ways to protect networks against such fiber faults and reduce costs by more efficient use of protection bandwidth.
Existing protection switching systems usually involves higher level communications or signaling between nodes in the network using complex framed overhead channels or packet communications.
Designing networks that are automatically protected against multiple worst-case fiber breaks can be difficult and expensive. As a result, many network protection schemes typically only provide automatic protection against single fiber faults. The reasoning behind this is that a repair crew will be dispatched immediately after a single fault and hopefully fix the problem before another fault occurs. Many of the overall transport line and network availability calculations are dominated by the probability of second fault occurring before the first fault is repaired.
Major disasters, like earthquakes and hurricanes, can often cause multiple fiber breaks in a network. While no system can protect against every contingency, having a network that can automatically reconfigure and recover from multiple fiber faults will greatly improve overall availability.